EP0535332A2 - Refrigeration apparatus, especially multi-temperature refrigerator - Google Patents

Abstract

Multi-temperature refrigerator, with a single-circuit refrigerating machine, the evaporators of which, which are connected in series, are assigned to a freezing compartment and a refrigerating compartment, and the control of which controls the refrigerating machine 0periodically depending on the evaporator temperature in the refrigerating compartment in such a manner that, before each restart of the refrigerating machine, a defrosting of the evaporator in the refrigerating compartment takes place, and with a fan which circulates the air in the refrigerating compartment in a temperature-dependent manner and which is switched on by a switch (21), which reacts to the ambient temperature of the appliance, only in the event of ambient temperatures being above the normal room temperature (20 DEG C), while the control (19) is additionally equipped with a sensor (19'') which detects the air temperature in the refrigerating compartment (11) and with the aid of which it switches off the refrigerating machine (15) when the lower switching point in the refrigerating compartment (11) is reached. <IMAGE>

Description

The invention relates to a refrigerator, in particular a multi-temperature refrigerator, with a single-circuit refrigerator, the evaporators connected in series are assigned to a freezer compartment and at least one refrigerator compartment and the controller periodically controls the refrigerator depending on the temperature in the refrigerator compartment so that before each The chiller is restarted and the evaporator defrosted in the refrigerator compartment, as well as with a fan that circulates the air in the refrigerator compartment depending on the temperature.

In cooling devices of the type described above, it is customary to use so-called “constant-on controllers”, the sensors of which detect the temperature of the evaporator in the cooling compartment and whose automatic upper defrost point above the freezing point permits automatic defrosting of this evaporator.

Such constant-on controllers have proven themselves because of their simple construction and their very reliable function at normal room temperature and have therefore found widespread use in general in cooling devices of the type mentioned. However, they have the disadvantage that their control behavior changes considerably even with small seasonal deviations in the room temperature at the installation site of the device. So at low room temperatures - due to the then lower heat incidence in the heat-insulated cooling compartment of the device and the resulting lower switch-on frequency and running time of the compressor of its refrigeration machine - there is a risk that the temperature in the freezer compartment will rise above the permissible highest value, so that stored in the freezer compartment Can be well damaged and spoiled.

In contrast, an increase in the room temperature caused by summer weather conditions has a less disadvantageous effect, since the temperature in the freezer compartment drops more because of the higher heat input in the refrigerator compartment and the resultant greater switching-on frequency and longer running time of the refrigerator; however, this has no adverse consequences for the goods stored in the freezer. However, if the door of the refrigerator is opened frequently, the parts of the room air that are cooled far below the dew point of the air and the refrigerated goods stored there may become heavily condensed due to the relatively high moisture content of the ambient air surrounding the unit.

In order to solve the difficulties that arise at low room temperature, it has already been proposed to increase the temperature in the normal cooling compartment by counter-heating and thus to increase the number of times the refrigerator is switched on and on. In the case of a solution which has become known with the DBP 943 169, a light bulb serving as lighting for the cooling compartment is used for counter-heating, the heating output of which, when the ambient temperature decreases, is controlled in inverse proportion by a switch which detects the outside temperature at the installation site of the device.

In a further solution known from DE-OS 39 04 216, when the temperature rises in the freezer compartment, a heat sensor arranged there should switch on a fan mounted in the refrigerator compartment and controlled by a microprocessor in order to circulate the air in the refrigerator compartment and thus the room temperature in the case of unfavorable outside temperatures Keep the freezer compartment at the set temperature specified there.

However, while in the first case the efficiency of the cooling device is considerably impaired by the supply of thermal energy in the cooling compartment, in the second case a complex electronic circuit is necessary in order to achieve the desired success. In this case, due to the heat sensor in the freezer compartment for controlling the fan operation, the proposed solution is also relatively inert.

Proceeding from this known prior art, the object of the invention is to create a multi-temperature refrigerator with a control system which, in particular, enables the control behavior to be adapted in a simple manner in a range that deviates from the standard temperature far upwards and thus make them independent of these temperature fluctuations.

This object is achieved according to the present invention in that a switch reacting to the ambient temperature of the device switches the fan on only when the ambient temperature is above normal room temperature (20 ° C.) and in that the controller is additionally equipped with a sensor that detects the air temperature in the cooling compartment , with the help of which he switches off the chiller when the lower switching point in the refrigerator compartment is reached.

With the help of the switch which responds to high room temperatures according to the invention and which only starts the fan at higher temperatures than the normal room temperature, it is possible to use the cooling devices equipped therewith without additional measures even at high ambient temperatures, i.e. also under subtropical or even tropical temperatures To be able to use climatic conditions without having to accept the deviations in the control behavior of the devices that otherwise occur due to high outside temperatures. At the same time, it is achieved that the moisture accumulating at high outside temperatures is precipitated as frost directly on the evaporator of the cooling space with the help of the air flow generated by the fan, without wetting the cold parts of the cooling space or the already cooled goods stored therein to any appreciable extent to have.

According to a particularly advantageous embodiment of the object of the invention, it is provided that the circuit of the fan can only be closed when the compressor of the refrigerator is switched on.

In this way it is ensured that the temperature in the cooling room cannot drop further if the refrigerator is stopped when the lower switch-off point is reached and the temperature can drop below the lower limit due to further air circulation via the then still very cold evaporator.

In order to ensure that the temperature limits in the cooling compartment are strictly observed, it can be provided according to an advantageous development of the subject matter of the invention that the fan is additionally provided with a time delay switch, with the aid of which its running times are offset from the running period of the refrigerator.

Fig. 1

einen Mehrtemperaturen-Kühlschrank mit einem in dessen Kühlfach angeordneten, in Abhängigkeit von der Außentemperatur gesteuerten Ventilator in schematischer Schnittansicht,

Fig. 2

ein Diagramm, aus dem das Temperaturverhalten in den einzelnen Fächern des Mehrtemperaturen-Kühlschranks bei einer Außentemperatur von + 16°C hervorgeht und

Fig. 3

ein der Fig. 2 entsprechendes Diagramm, jedoch bei Außentemperaturen von + 32°C.

The invention is explained in the following description with reference to an exemplary embodiment of a multi-temperature refrigerator shown in simplified form in the accompanying drawing and several diagrams from which the temperature behavior in the compartments of the cooling device can be seen at different room temperatures. Show it:

Fig. 1

a multi-temperature refrigerator with a fan arranged in its cooling compartment and controlled as a function of the outside temperature in a schematic sectional view,

Fig. 2

a diagram showing the temperature behavior in the individual compartments of the multi-temperature refrigerator at an outside temperature of + 16 ° C and

Fig. 3

a diagram corresponding to FIG. 2, but at outside temperatures of + 32 ° C.

A two-temperature refrigerator designated by 10 in FIG. 1 is equipped with a normal freezer compartment 11 and an overlying freezer compartment 12, both of which can be locked separately with doors 13 and 14 assigned to them. At the bottom of the two-temperature refrigerator 10, an encapsulated compressor 15 of a single-circuit refrigeration machine of a conventional type is arranged in a recess recessed in the rear area from its heat-insulated housing, the individual elements of which are not shown for the sake of simplicity of illustration. The compressor 15 is connected via lines 16 and 17 to the network of a power supply. In line 17 there is a switch 18 of a controller 19 which detects both the air temperature inside the refrigerator compartment 11 and its evaporator temperature. For this purpose, the controller 19 is equipped with two temperature sensors 19 'and 19' ', of which the one labeled 19' is assigned to the evaporator of the cooling compartment 11 and switches the controller 19 on, during which the temperature sensor 19 'detecting the air temperature in the normal cooling compartment 'turns off the controller.

A fan 20 is also arranged in the interior of the cooling compartment 11, the drive motor of which is switched by means of a switch 21 as a function of the temperature of the atmosphere surrounding the cooling device 10.

The two switches 18 and 21 are switched so that the circuit of the fan 20 is closed via the switch 21 only when the switch 18 controlling the compressor 15 of the refrigeration unit is also closed.

From the curve sections shown in the diagrams according to Figures 2 and 3 in the form of so-called "refrigerator characteristics", the temperature profile in the freezer compartment "TV" and in the normal refrigerator compartment (TM) of a single-circuit two-temperature refrigerator can be used depending on the room temperature and the detect the relative duty cycle (RED) of his cooling unit affected by this. The term “relative duty cycle” is to be understood as the ratio of the duty cycle of the compressor of the refrigerator to its downtimes, expressed in percent, which increases with increasing room temperature.

In the lower section of the diagrams recorded once at a room temperature of + 16 ° C (Fig. 2) and once at a room temperature of + 32 ° C (Fig. 3), the relative duty cycle of the compressor (RED) is above the middle one Temperature (TM) is plotted in the normal refrigerator compartment, while the temperature curve (TV) depending on it is plotted in the freezer compartment.

wobei unter Q die übertragene Kälteleistung in W, mit α die Wärmeübergangszahl in W/m²K, A die Verdampferfläche in m² und unter Δ T die Temperaturdifferenz in K zu verstehen ist. Unter Verwendung des Ventilators im Normalkühlfach ergeben sich somit die B bezeichneten, gestrichelt eingezeichneten Kurven. Es ist dabei zu erkennen, daß die Erhöhung des Wärmeübergangs zu einer kleineren Temperaturdifferenz zwischen der Lufttemperatur im Normalkühlfach und dessen Verdampferoberfläche führt. Dies hat zur Folge, daß die Lufttemperatur entsprechend der Änderung von 1 nach 2 kälter wird. Ferner ergibt sich daraus, daß bei konstanter Temperatur im Normalkühlfach die relative Einschaltdauer des Verdichters (RED) kleiner und die Temperatur im Tiefkühlfach entsprechend der Differenz von 1 nach 3 wärmer wird.Here, the fully drawn curves labeled A, the refrigerator characteristics describe the normal state, i.e. with the usual free convection. On the air in the fridge a circulating fan increases the cooling capacity because the heat transfer is increased by increasing the heat transfer coefficient α. It applies

$\text{Q = α x A x Δ T}$

where Q is the transferred cooling capacity in W, α is the heat transfer coefficient in W / m²K, A is the evaporator area in m² and ΔT is the temperature difference in K. Using the fan in the normal refrigerator compartment results in the B-denoted, dashed curves. It can be seen that the increase in heat transfer leads to a smaller temperature difference between the air temperature in the normal cooling compartment and its evaporator surface. As a result, the air temperature becomes colder according to the change from 1 to 2. It also results from the fact that at constant temperature in the normal freezer, the relative duty cycle of the compressor (RED) is shorter and the temperature in the freezer becomes warmer according to the difference from 1 to 3.

It follows from this that the use of a fan in the normal refrigerator compartment contributes to increased performance and to the avoidance of internal condensation at high ambient temperatures and high air humidity. Switching on the fan at a low ambient temperature is therefore not required or even disadvantageous, since the dependent temperature in the freezer compartment may rise above the permissible limit. For this reason, it makes sense to switch the fan inside the normal cooling compartment - as proposed with the present invention - via the thermostat 22, which controls the fan depending on the temperature of the ambient air surrounding the device. In order to avoid an undesirable temperature drop in the normal cooling compartment which then results from the increase in the heat transfer coefficient on the evaporator, the compressor 15 is switched off via the controller 19 as soon as an air temperature corresponding to the lower switching point is reached on the sensor detecting the air temperature in the normal cooling compartment. The controller 19 thus switches off the compressor of the refrigeration machine as a function of the air temperature in the normal cooling compartment and switches on via the temperature of the evaporator surface in the normal cooling compartment.

At high ambient temperature and high air humidity, with the help of the air flow forced by the fan in the normal refrigeration compartment 11, a large part of the moisture entering the atmosphere surrounding the device when the door 13 is opened is transported to the evaporator and specifically deposited there as frost. The remaining portion of the air humidity, which is temporarily deposited on the cold refrigerated goods and cold parts inside the normal refrigerator compartment, is quickly absorbed by the then prevailing air flow and also transported to the evaporator, from which the ripening that has developed there completely defrosts during the idle time of the unit.

Claims (3)

Refrigerator, in particular multi-temperature refrigerator, with a single-circuit refrigerator, the evaporators connected in series are assigned to a freezer compartment and at least one refrigerator compartment and the controller controls the refrigerator periodically in dependence on the evaporator temperature in the refrigerator compartment in such a way that defrosting occurs before each restart of the refrigerator of the evaporator takes place in the cooling compartment, and furthermore with a temperature-dependent fan which circulates the air in the cooling compartment, characterized in that a switch (21) which reacts to the ambient temperature of the device causes the fan (20) to lie only above the normal room temperature (20 ^o C) Enables ambient temperatures and that the controller (19) is also equipped with a sensor (19 '') which detects the air temperature in the cooling compartment (11), with the aid of which it switches off the refrigerator (15) when the lower switching point in the cooling compartment (11) is reached. Cooling device according to claim 1, characterized in that the circuit of the fan (20) can only be closed when the compressor of the refrigeration machine (15) is switched on. Cooling device according to claim 2, characterized in that the fan (20) is additionally provided with a time delay switch, with the aid of which its running times are offset from the running periods of the refrigerating machine.

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